Due to recent outbreaks of highly infectious disease attributable to airborne microorganisms in indoor air, the need has arisen for apparatus and rapid methods for detecting and collecting infectious airborne microorganisms such as viruses, bacteria, molds, yeasts, and spores for rapid identification. Sneezing, coughing, and even speaking by an individual suffering from pulmonary tuberculosis, for example, can result in the release of large quantities of mycobacteria-containing particles into indoor air. The larger particles fall to the floor or other surfaces. These become dust-associated mycobacterial particles and are not believed to pose a serious health risk due to their larger size. The smaller mycobacterial-containing particles, however, undergo rapid evaporation and remain airborne indefinitely. Sub-micron size particles pose a serious risk of lower respiratory tract infection and disease. Tubercle bacilli are exceptionally hardy; the long-term viability of these microorganisms is unknown.
Thus a special need for detecting and collecting infectious airborne microorganisms for rapid identification exists, especially in places where disease can be readily spread from one person to another, such as in prisons, hospitals, homeless shelters, classrooms, and the workplace.
Presently, however, no method or apparatus exists to detect and collect airborne microorganisms in indoor air for rapid identification. The most commonly used protective device is the HEPA (High Efficiency Particulate Air) filter. This device is unsatisfactory because it becomes clogged with living, breeding microorganisms and offers little or no protection from microorganisms which are smaller than its smallest orifice. These pathogenic microorganisms can bypass the HEPA filter as well as nasal and throat defenses and reach the lungs. Also, the HEPA filter is useful only if the microorganisms are culturable. Many are not.
An alternative to the HEPA filter is a system which kills, but does not collect, pathogenic microorganisms by subjecting them to ultraviolet radiation. This system is not widely used, however, because it exposes workers and others to potentially harmful radiation. The room air sterilizer claimed in U.S. Pat. No. 5,225,167 (Wetzel) combines the HEPA filter with a germicidal ultraviolet lamp. The lamp is positioned so as to kill the microorganisms trapped in the HEPA filter without exposing workers and others to radiation. This system does not collect the microorganisms for subsequent identification and offers no protection from sub-micron size microorganisms which are small enough to pass through the smallest orifices of the HEPA filter. For example, many viruses are 300-400 Angstroms in size; much smaller than the orifices of a HEPA filter.
Other alternatives are the impactors and impingers. An impactor drives diseased air against a series of sampling plates having successively smaller holes. The largest microorganisms are collected at the first stage and smaller microorganisms are collected at later stages. While impactors collect microorganisms for identification, they, like the HEPA filter, suffer from the drawbacks of allowing sub-micron size microorganisms to escape and of dealing with living microorganisms.
The liquid impinger employs a compressor to draw diseased air at nearly sonic velocity into a liquid medium. This methodology, however, disintegrates many cells, which distorts and impedes the detection and collection of the pathogens, particularly those of less than one micron in size. Moreover, the necessity of a compressor renders a liquid impinger impractical for hospital use.
Consequently there remains a need for a method and apparatus for detecting the presence of airborne infectious microorganisms in indoor air and collecting these microorganisms for rapid identification which can be used in any indoor living or work space.
An additional problem that has been experienced in the process of collecting airborne microorganisms in a liquid medium as described above is that the concentration of microorganisms in the liquid is too low to allow meaningful analysis. Consequently there remains a need for a method of processing a sample of microorganisms captured in a liquid medium such that the sample is sufficiently concentrated to allow meaningful analysis.